Ergonomic requirements

Dimensional parameters

Before establishing dimensional requirements, it is necessary to differentiate between the device as a whole and the braille cell.

For the dimensions of the product, as a modular product is proposed, the total dimensions will vay depending on the number and configuration of the different modules. As clear and reference examples, it is posible to draw on the different models existing in the market and also on to the traditional keyboards.

On the other hand, the dimensions of the braille cell will be adapted to those describe in document "B1. Parámetros dimensionales del braille V1” provided by the O.N.C.E association whose specification is as follows: (www.once.es, s.f.)

Being:

a = distance between the center of a point and the center of the horizontally contiguous point.

b = distance between the center of a point and the center of the vertically contiguous point.

c = distance between the center of a point and the center of the homologous point of the horizontally contiguous cell.

d = distance between the center of a point and the center of the homologous point of the vertically contiguous cell.

e = diameter of the points

f = height of the points, recommended between 0.2 and 0.5 mm.

Whose values will depend on the diameter of the opints, according to the following table:

e (mm) ; a (mm) ; b (mm) ; c (mm) ; d (mm)

1,2 ; 2,4 ; 2,4 ; 6 ; 10

1,3 ; 2,45 ; 2,45 ; 6,13 ; 10,18

1,4 ; 2,5 ; 2,5 ; 6,26 ; 10,36

1,5 ; 2,55 ; 2,55 ; 6,39 ; 10,54

1,6 ; 2,6 ; 2,6 ; 6,52 ; 10,72

1,7 ; 2,65 ; 2,65 ; 6,65 ; 10,9

1,8 ; 2,7 ; 2,7 ; 6,78 ; 11,08

1,9 ; 2,75 ; 2,75 ; 6,91 ; 11,26

Therefore, the final dimensions of the device will depend dundamentally on the number of modules or braille cells, toghether with the actuator mechanism, the support and the control and power modules that will be discussed later.

Weight

The device should be as light as possible, so its weight will try to be limited. All this guaranteeing its portability and manageability without reliability and durability being affected.

Compatible materials

According to its classification (Surface device B/C) as set out in the table “Table 1: ISO 10993-1 Biocompatibility Testing Selection Criteria” the device must be of a material, capable of being printed in 3D, that passes the cytotoxicity, sesitization and irritation test or intracutaneous reaction. (platform.ubora-biomedical.org, s.f.)

Color palette

The colors used in the device, in accordance with the provisions of the ONCE document "Accessibility for people with blindness and visual impairment" based in turn on UNE standards, should be combined as some of the proposed color/contrast alternatives to increase its visibility. The recommended combinatins are: (Blanco Sanz, y otros, 2004)

Details ; Big surfaces

White ;Dark blue

Black ; Yellow

Green ; White

Red ; White

Blue ; White

Black ; White

Yellow ; Black

White ; Red

White ; Dark green

White ; Black

Use and functionality requirements

Control

The control of the device will be carried out by an auxiliary device, either a microporcessor or microcontroler. That auxiliary device must be able to guarantee the correct functioning of the device as a whole, in accordance with the braille reading speed and therefore the refresh rate.

Drive

The general drive will be carried out with secundary elements like linear actuators, rotating motors or similar. Those elements must be able to guarantee that the device functions correctly according to the other requirements.

Power

The power method, which in all cases will be carried out from an external source, will be adjusted to the needs and peculiarities of the control option finally chosen. All this ensuring that the device will remain active for as long as the user requires without presenting any problems.

Safety

The device must ensure that, during its design and manufacture, the following are taken into account:

• The knowledge and physsical and medical contidions of the end users.
• That its use will not cause damage to its users and therefore will not put their health at risk.
• Thar its characteristics and features will not be modified during transport and storage.

References:

www.once.es. (2019). Obtenido de www.once.es: https://www.once.es/servicios-sociales/braille

platform.ubora-biomedical.org. (s.f.). Obtenido de platform.ubora-biomedical.org: https://platform.ubora-biomedical.org/resources/937676d7-9a48-4867-a491-f2bb8edad2ba

Blanco Sanz, R. M., Blanco Zárate, L., Luengo Jusdado, S., Pastor Martínez, G., Rivero Coín, M., Rodriguez de Luengo, R., & Vicente Mosquete, M. J. (2004). Accesibilidad para personas con ceguera y deficiencia visual. Madrid. Obtenido de https://www.diba.cat/c/document_library/get_file?uuid=1f52cb9c-5861-415d-95f3-2d0c710d4dc4&groupId=7294824